The SPC also warns that the concomitant use of rifampicin with other antibiotics causing vitamin K dependent coagulopathy such as cefazolin (or other cephalosporins with N-methyl-thiotetrazole side chain) should be avoided as it may lead to severe coagulation disorders, which may result in fatal outcome (especially in high doses).
It also notes that severe cutaneous adverse reactions, which can be life-threatening or fatal, have been reported (unknown frequency).